Abstract : The core idea of utilitarianism for Bentham is to establish that only individual utilities count in social welfare. There can be two distinct interpretations of this apparently simple principle. According to one view, individual utilities represent the basic information for the calculation of social welfare: this is how utilitarianism works. According to a second view, social welfare is maximized if and only if individual utilities are maximized: this is what justifies utilitarianism. This aim of this paper is to show: that these two interpretations should not be confused; that they correspond to distinct definitions of welfarism; that they are likely to conflict; and that as a consequence we can draw important and surprising conclusions for political philosophy and economic science. One such conclusion is that fairness should be prior to goodness in a consistent Benthamian doctrine.